Small aircraft on INS approach in IMC gets 50' below MDA and receives low altitude alert from ATC.

Attributes
ACN	132282
Time
Date	198912
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dwh
State Reference	TX
Altitude	msl bound lower : 450 msl bound upper : 500
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dwh
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial pilot : cfi
Experience	flight time last 90 days : 30 flight time total : 3600 flight time type : 200
ASRS Report	132282
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure other spatial deviation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Flying localizer DME approach at 500', hit wind shear. Plane went to 450' before being corrected back to 500'. Tower advised 'low altitude alert--check altitude.' approach and landing were completed at dwh. Ceiling was approximately 510-550'. Tower did not say anything else about low altitude alert after landing. Should fly approach higher to allow for downdraft.

Original NASA ASRS Text

Title: SMA ON INS APCH IN IMC GETS 50' BELOW MDA AND RECEIVES LOW ALT ALERT FROM ATC.

Narrative: FLYING LOC DME APCH AT 500', HIT WIND SHEAR. PLANE WENT TO 450' BEFORE BEING CORRECTED BACK TO 500'. TWR ADVISED 'LOW ALT ALERT--CHK ALT.' APCH AND LNDG WERE COMPLETED AT DWH. CEILING WAS APPROX 510-550'. TWR DID NOT SAY ANYTHING ELSE ABOUT LOW ALT ALERT AFTER LNDG. SHOULD FLY APCH HIGHER TO ALLOW FOR DOWNDRAFT.

Data retrieved from NASA's ASRS site as of August 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.